Microbially enhanced oil recovery

Reviving natural resources, naturally

Tiny and invisible, bacteria are often maligned as 'bugs' that cause diseases in humans and animals. Little do we know of how wonderfully they help sustain life on earth. As the base of the food chain in many environments, they do the most inane and tedious of jobs–from breaking down dead, organic matter and recycling natural resources to putting that tang in yoghurt, and that sour taste in dough bread. And now, scientists at TERI have developed ways of utilizing these bacteria to extract oil from 'sick' or less productive oil wells and putting them back in business.

Tackling critical needs

Preparing nutrients for injection into the oil well

Ageing of wells is a perpetual and crucial concern that the global oil industry faces. Thousands of oil wells lie abandoned – they are either unproductive or yield oil in insignificant quantities. An oil well becomes sick when approximately 30% of oil in place has been recovered. The reason: natural gas in the reservoir (responsible for pushing oil up to the mouth of the well) diminishes in quantity and loses pressure because of deep extraction. As a result, the oil flow decreases and eventually stops. These so-called dead or sick wells still have a substantial quantity of oil left in them. Conventional methods of recovery are extremely expensive and costs can vary from 140 000 to 200 000 dollars per well.

However, as oil reserves dry up globally, the depth of wells increases, and temperatures inside the reservoirs also increase (it varies between 80 oC and 120 oC), these methods prove ineffective and the task becomes more challenging.

From 'unwell' to 'oil well'

Mixing nutrients with microbes

The MEOR (microbial enhanced oil recovery) mechanism of extracting oil from less productive wells has solved an age-old problem that perplexed the oil industry the world over. Also called the huff-puff method of oil recovery (it involves injecting microbes and then sucking up oil), it extracts over three times the oil than any other conventional process.

After these microbes are injected into an oil well, they take close to a fortnight to do their job. What happens in the oil reservoir during the incubation time makes for interesting study. To understand it better, one needs to visualize rocks with pores, much like a honeycomb. Oil, being viscous, is trapped in these pores. These microbes produce carbon dioxide and methane, gases that enter the pores and squeeze out every ounce of oil. They also produce bio-surfactants (detergent-like compounds) that reduce the tension between oil and the rock surface and help release the oil. The reaction of these microbes in oil also releases alcohol and volatile fatty acids. The alcohol reduces the viscosity of oil, making it light enough to flow out. The fatty acids solubilize the rock surface and thus push oil off them. The MEOR process of oil recovery actually offers more than the advantages of conventional methods of oil recovery plus the added strengths of the microbes.

Injecting selected microbes into the oil well

These microbes produce carbon dioxide and methane, gases that enter the pores and squeeze out every ounce of oil. They also produce bio-surfactants (detergent-like compounds) that reduce the tension between oil and the rock surface and help release the oil. The reaction of these microbes in oil also releases alcohol and volatile fatty acids. The alcohol reduces the viscosity of oil, making it light enough to flow out. The fatty acids solubilize the rock surface and thus push oil off them. The MEOR process of oil recovery actually offers more than the advantages of conventional methods of oil recovery plus the added strengths of the microbes.

Beneficiaries

Wells of the ONGC (Oil and Natural Gas Corporation) in Gujarat have been revived, thanks to this technology, and are functioning again. The MEOR technology, when applied in 25 oil wells of ONGC, extracted 4500 cubic metres of oil from one of the sick wells, translating into revenues of more than 675 000 dollars. The Company plans to use the technology for other sick oil wells in Gujarat and Assam. Its benefits such as cost-effective use and environment-friendly nature have generated interest among oil firms in the Middle East and other oil-producing countries.

Funded partly by the Department of Biotechnology, Government of India, the project received financial assistance of 10 million rupees from ONGC, and technical and infrastructural support from the IRS (Institute of Reservoir Studies), a research wing of ONGC. T E R I and ONGC have already jointly applied for this technology.

Applications/benefits

Oil recovered through TERI's microbial technology has helped bring down the cost of oil substantially. Depending upon the nature of recovery, the price of each barrel of oil can decrease by as much as 35%–40%. Moreover, the environment-friendly nature of this form of oil recovery gives it an edge over other conventional methods. The possibilities that these invisible, living organisms offer us are immense and still not fully tapped.

A technological breakthrough

Microbial biotechnology came to the rescue when researchers at TERI cultured a set of microbes that could survive temperatures as high as 90 oC, air pressure up to 140 kilograms per square centimetre, and strong salinity with concentration levels ranging from 4% to 8%. Techniques used earlier for oil recovery employed microbes that could bear temperatures only up to 65 oC. T E R I cultured these stronger bacteria in simulated conditions of oil wells complete with high temperature, high pressure, and heavy salt concentration. The product was successfully tested in oil wells in Gujarat and the rest, as they say, is history.